By the end of today, Royal Mail's mail centre at St Rollox in the east end of Glasgow will have processed 2.6 million items.
That's pretty standard for this time of year.
But as well as the usual problems of incomplete addresses and missing post codes, the sorting machines are at risk because we love to send glittery cards.
"When people don't seal down their envelopes, glitter falls out into the machines and it can clog up some of the filters and block some of the beams," mailman Scott Young explains.
That's why Henry the vacuum cleaner is a vital member of the team.
Scott vacuums excess glitter from the sorting machines before it becomes a problem
"We increase our maintenance to clear all the glitter and dust away," Scott explained.
No-one is saying glitter's banned. But we can help by sealing down envelope flaps properly.
It's a new public service message to add to the routine ones about wrapping up parcels properly, and always using the full address.
"In particular, the post code," says Royal Mail's delivery director for the west of Scotland Gerry McAuley.
"That will help us sort the mail to the right town, and deliver it to the right address."
Tomorrow (Thursday 18 December) is the last day for posting Christmas cards second class.
"Thereafter they need to switch to first class," Mr McAuley explains.
"They can post first class up to Saturday 20th December.
"For any last minute cards or parcels that people have forgotten about, they can use Special Delivery up to 23rd December. And that will get there in time for Christmas."
And as well as the possible risk to the technology, there is a human side to the glitter story.
"When you deal with large volumes of letters by hand you can get glitter in your hair, and on your clothes," postie Conor McCartney told the BBC's Reporting Scotland programme.
"When you go home, your missus says 'Why have you got glitter all over you? Have you been talking to other girls?'"
"It's the letters, honestly. It's sorting all the letters," he laughs.
"Hopefully she believes me."
sniff sniff